The present invention relates to interpenetraring polymer networks formed from an acrylic-containing polysiloxane and an olefinic organic monomer. More particularly, the present invention relates to resinous silicone block copolymers reinforced by in situ polymerization of an olefinic organic monomer such as styrene.
Interpenetrating polymer networks (IPN's) are a unique type of polyblend synthesized by swelling a polymer with a monomer and activating agents, and polymerizing the monomer in situ. If one polymer is elastomeric and one polymer plastic at use temperature, the combination tends to behave synergistically, and either reinforced rubber or impact resistant plastic results, depending upon which phase predominates. See, for example, Polymer Blends and Composites, J. A. Manson and L. H. Sperling, pages 237-270, Plenum Press (1976).
Dietz, U.S. Pat. No. 2,965,593, discloses intimate homogeneous mixtures prepared by dispersing a polydiorganosiloxane substantially free of polymerizable olefinic groups in a vinyl monomer.
Bluestein, U.S. Pat. No. 4,014,851, discloses a polymer-filled vinylorganopolysiloxane dispersion comprising a continuous phase of an essentially ungrafted vinylorganopolysiloxane fluid having dispersed therein a discontinuous phase comprising finely divided solid particles of an ungrafted polymer prepared from an organic monomer having aliphatic unsaturation or a mixture of such monomers polymerized in the presence of said vinylorganopolysiloxane.
The present invention is based on the discovery that improved silicone resins can be prepared by forming an interpenetrating polymer network of said resin and an olefinic monomer. That improved resins could be obtained in such a manner was quite unexpected in view of the fact that both silicone resins and thermoplastics formed from vinyl monomers are generally quite brittle.